display! display issues

[Dahaka7172]

hi there,i have a dell 990 with i5 2500(non k),recently i started facing a weird issue(mostly with freesync on) where at first start dell logo shows and pc boots but at second boot monitor stays black.sometimes it takes 3 or 4 boot(power button press after 1,2 light appears<hdd lock) then monitor shows,also sometime screen stays black but when windows boots up display turns on and it works.i noticed that in device manager there's another monitor on my gpu(rx 570) with res of 64x64, i think maybe when i boot my pc up it tries to use that monitor, but on win7 theres no unknown monitor but when i change display hz from 75 to 60 for test brightness flickers. check the screenshots 
specs 
dell 990(a24 bios)
i5 2500(non k)
16GB ddr3 1333
msi armor rx 570 oc 
sorry for bad english!